Technical Abstract:
Perennial pepperweed (Lepidium latifolium) is a creeping rooted exotic weed that has infested riparian areas, native hay meadows and agronomic fields throughout the western United States. Perennial pepperweed is a highly invasive weed that causes management and economic problems through the loss of diversity and quality forage. In recent times there has been an increased interest in biologically controlling this aggressive weed through grazing management with sheep or goats. We investigated the grazing of perennial pepperweed by goats using eight 0.1 hectare enclosures in a dense perennial pepperweed infestation in northwestern Nevada. Four of the 0.1 hectare enclosures were grazed and combined with various herbicidal treatments, while the remaining 4 enclosures were grazed throughout the summer and seeded to the perennial grass, tall wheatgrass (Elytrigia elongata). Heavy grazing of perennial pepperweed decreased forage yield by 78%, yet did not decrease the number of perennial pepperweed plants in the plots. The control of perennial pepperweed using the grazing and herbicide treatments together was not significant (P = 0.05) compared to the herbicide treatments alone. Grazing perennial pepperweed as a control method followed by seeding was unsuccessful due to the fact that the sprouting perennial grass seedlings could not compete with the dense creeping rooted perennial pepperweed. The suppression of perennial pepperweed with the use of selective herbicides combined with the seeding of a competitive perennial grass, such as tall wheatgrass, was significantly (P = 0.05) more successful than the goat grazing treatments combined with seeding the same perennial grass.